Questions tagged [luminosity]

Luminosity is the energy radiated from a body per second.

74 questions
28 views

How to convert contrast ratio to number of stops?

I have read an article from the below link about the human eye sensitivity and came to know that its dynamic contrast range is 1000000:1 or in other words 30 stops. They also mentioned static contrast ...
35 views

Luminosity of the sun

How is it that the total power generated by nuclear reaction in the core of Sun exceeds its total luminosity? Where does the difference go?
27 views

Magnetic flux density compard to other definition of flux

With regards to flux i have always assumed it was defined as $$(1) Something/m^2s$$ For instance $Luminosity/(4\pi r^2)$ Is an example of radiation flux. Why then is faradys law often cited as the ...
21 views

Luminostiy, Flux, Intensity definitions and meaning

I am taking astrophysics course and we are constantly talking about Luminosity,Brightness,Intensity,Flux etc. I thought that I understand the idea properly but I see now that I dont. Intensity is the ...
96 views

Why is the relation between luminosity distance $d_L$ and comoving distance $\chi$ $d_L=\chi/a$?

The textbook (Scott Dodelson, Modern Cosmology, Section 2.2 Distance, Page 35-36) states as follows: Another way of inferring distances in astronomy is to measure the flux from an object of known ...
94 views

Luminosity of a white dwarf

Why in an H-R diagram the white dwarfs are at the bottom left? I understand that they would have a high temperature when they are formed, and so at that instant shouldn't they have a high luminosity ...
57 views

Finding the distance to a distant star using standard candles

I understand how we can measure the luminosity of a close star through absolute and apparent magnitude, because we can easily find the distance through trigonometric parallax. What I have understood ...
125 views

What is the closest distance for an undiscovered old neutron star and how long would it take to get here? To help people scared of neutron stars

This is to help people who are scared of neutron stars. My questions are What is the faintest a neutron star could be How close could it be and not yet be detected How long would it take to get here ...
26 views

Stephan Boltzmann law

I was preparing for INAO when I came across the application of Stephan Boltzmann law...it's says that energy absorbed per unit time by a planet is Flux times πr^2. But why did we multiply with πr^2 or ...
29 views

Do bigger stars emit higher amplitude waves?

So I’ve been reading about luminosity and I get the concept of the size and temperature determining the intrinsic brightness and total energy emission of the star. I also understand how the further ...
48 views

Where can I find values for apparent brightness of stars?

I'm in high school and doing a project. I want to calculate the distance to stars using their luminosity and apparent brightness, from the equation $b=\frac{L}{4 \pi d^2}$. I have found values for ...
100 views

106 views

How to define the light “color” from a given spectral distribution?

The following question may be naive and incomplete in some way I don't know. I'm not a specialist on spectroscopy, colours and light curves, color spaces, etc. Suppose you have a simple power-law ...
587 views

Radiation pressure in terms of luminosity?

My class slides have given me the following equation for $P_{rad}$: $P_{rad}=\frac{4\sigma T^4}{3c}$, where $\sigma$ is the Stefan-Boltzmann Constant. I know that radiation pressure is pressure on a ...
175 views

Distribution of wavelengths of monochromatic light sources in expanding FLRW universe

I'm looking for the distribution of all wavelengths (or frequencies) of light that a stationary observer would receive at his location (at $r = 0$ and time $t_0$), from light sources emitting a single ...
While writing my notes on cosmology, I found this little puzzle, which isn't described in any of my books on general relativity. Consider a flat space ($k = 0$) filled with dust-like matter, of ...